An Assistant of Strange Rationale
by Alatar Maia
Summary: (Third in the 'Strange' series. These titles are getting a bit difficult). Percy was just trying to finish the quest and get his memories back. He's doing fairly well with both, all things considered. Then Hazel's magical horse showed up again, and it brought a friend with it who was more than appearances suggested.


**Eyyy guess what it's part three of this series! This one takes place during The Son of Neptune, again more towards the end. Basically the same idea as the last one, I guess.**

 **Disclaimer: I don't own Heroes of Olympus.**

* * *

They'd been having a nice, peaceful dinner - for _once_ \- when the gryphons decided to show up again. There was only one so far, but Hazel didn't doubt that more were coming.

Now they were on the edge of a pier, with no way to get to where they needed to be. The Feast of Fortuna was in only _hours,_ not days, and they still had no idea how to _get_ to Hubbard Glacier and Alcyoneus, much less defeat him and unchain Thanatos.

Hazel had been put off-kilter by the way the town had changed in the seventy years since she'd been there, but the looming threat made her immediately snap back to the present, senses sharpening. Sharp enough to catch the faintest trace of a horse's whiny.

Hazel took the faint hope. "Arion!" She shouted, making Percy and Frank look at her sharply.

"What are you-" Percy didn't have time to finish before Arion was standing in front of Hazel, steam rising in his wake. "Whoa!"

"Good horse!" Hazel threw her arms around Arion's neck, hugging him in delight.

Frank had jumped backwards at the abrupt arrival and nearly fallen off the pier. "How-"

"He followed me!" Hazel stepped back, beaming. Arion's arrival couldn't have been timed better. "Because he's the _best horse ever_!"

"And he brought a friend." Percy was looking just behind Arion, where another horse was standing. "Another _magical_ friend, I'm guessing."

Hazel could tell why Percy thought that - normally, horses didn't have eight legs. This one had two for each one a regular horse might have had. It was looking back at Percy placidly.

"We have to go," Hazel said. "Now. Arion can get us to the glacier."

"Can all three of us fit?" Frank asked doubtfully. The second horse whinnied, and Percy looked surprised.

"Huh," he said. "Uh, that guy's offering to take one of us."

"Frank can sit with me," Hazel said, swinging herself up onto Arion's back and extending a hand towards Frank. "You're the one who's talking to him, after all."

Percy didn't seem bothered by the second horse's lack of tack or any sort of saddle, managing to mount with little difficulty. Arion shot off immediately, before Hazel could even think to ask whether the second would be able to keep up.

As it turned out, he could.

Percy's horse kept even with Arion across the water, eight legs working swiftly. Hazel felt like she was in her prime. _This_ was where she belonged, knowing where Arion was going to turn before he did, powerful and in control.

Frank, when she looked behind her, didn't seem to enjoy the ride quite so much. His cheeks were jiggling from the g-force and his eyes were squinted shut. His death grip around her waist, at least, assured her that he wouldn't fall off; with how fast Arion was going, she might not notice for fifty or sixty miles.

When he finally stopped, the temperature dropped. Arion had been moving so fast he'd generated his own bubble of heat. Percy's horse stopped as well, skidding slightly on the ice.

"How many superfast horses can there _be_?" Frank asked.

"No idea," Percy replied. "He says his name's Slepnir. Any of you ever heard of a horse in Roman mythology with that name?"

"It doesn't sound Roman at all. Or Greek," Hazel said. "I've never heard it before."

"That's what I figured," Percy said.

A boom interrupted them, a crack like lightning following it as a huge chunk of the glacier in front of them calved off, plummeting into the ocean. The noise from the splash hit them a second after they saw it happen, a thunderclap of noise that equaled the noise Arion made when he burst into subsonic speeds.

"We can't climb that thing!" Frank protested. Arion whinnied, and Slepnir made a noise that sounded almost like a laugh.

"Hazel," Percy said, "Your horse has a really dirty mouth."

"What did he say?" Hazel had to suppress the urge to laugh.

"Without all the cussing? He can get to the top." Percy glanced down at Slepnir, who nickered. "So can he."

"I thought they couldn't fly!" Frank sounded astonished. Arion's answering whinny was so angry that Hazel didn't need Percy's translation to know he was swearing.

"Hang on," she warned, before both horses took off again.

* * *

Once they got him into Canada, Alcyoneus was almost too easy to defeat.

Percy met them as they were halfway back to the glacier, riding Slepnir with the Fifth Cohort's eagle standard in his hand and pulling a chariot full of Imperial gold weapons and armor.

"Whoa," Frank said, impressed. "Where'd that come from?"

"The bottom of the ocean," Percy said. "I managed to get it all out of the water. Since when can you _shapeshift_?"

Frank explained hastily, as Hazel pulled him back onto Arion. Percy whistled once he'd finished. "Man. _I_ can't shapeshift!"

"You can breathe underwater and control water!" Frank protested. "That's a much cooler power."

"Fair enough," Percy allowed.

"Enough talking," Hazel said, still tingling with adrenalin. "We need to get back to New Rome." She didn't know if the army had already made a move on the camp, but if they had...

Frank and Percy immediately sobered. "Right," Frank said. "Is that chariot going to hold up? The last one fell apart."

"It's got Imperial gold wheels and axle," Percy said. "It should."

"We can't waste any more time." Impatient, Hazel pressed her heels to Arion's sides, and the horse took off like a shot.

* * *

The first chance Percy got to relax once fighting was done was during the ensuing feast. He'd managed to dart away, despite his new status as praetor, without anyone noticing.

He almost ran into Slepnir, thoughts drifting and taking him with them so that he didn't notice the horse until it was almost too late. Percy backed up quickly, nearly tripping over his new cape, and the horse snorted in a manner that was distinctly amused.

"Yeah, yeah, laugh it up." Percy had long ago gotten over any awkwardness he felt at talking to horses. "You're the one who came out of nowhere."

Slepnir didn't reply, but his eyes glittered in the light in a way that Percy could recognize as distinctly mischievous. He _shifted,_ for lack of a better word, form changing and warping until a boy who couldn't have been older than nineteen stood in front of Percy, wearing what might have been armor and a shit-eating grin.

Percy's grin had vanished. "Holy crap," he managed. "You're-" He'd _ridden_ that horse.

"Not a human," the boy said mildly. "You're not the only ones who can shapeshift, you know."

Percy realized his mouth was slightly open and shut it quickly. "You're saying you _normally_ look like a horse?"

"I _am_ a horse." The boy clarified. "Kind of like how your friend is human, but can turn into an animal."

Oh, geez. He'd ridden this guy. That sounded much more wrong than it had when Slepnir had been just a horse.

Slepnir's grin reappeared, as if he could guess what Percy was thinking. "Don't worry about earlier," he said. "I've carried people and pulled chariots before. If I minded, I wouldn't have let you."

"Uh...thanks, I guess?" Slepnir had helped them a lot in the battle. "Arion found you, right?"

"I found him," Slepnir corrected him. "I was looking for your camp, actually, but then I realized that you probably needed the help more than they did."

"What?" Percy froze. "You were looking for Camp?"

"Don't be like that," Slepnir said, grin fading slightly. "I was going to offer them help, to."

"Why?"

"You helped my family. There's a debt to be repaid."

Percy frowned. "Your family?" Who had he helped who might be related to a shapeshifting horse?

Slepnir nodded. "My shapeshifting...it's something I like to think I get from my father. Well, mother, technically, but he gets tetchy when I call him that." Amusement flickered in his eyes. "You met him last summer, before Hera took you away."

Percy was about to say that he didn't know what Slepnir was talking about, when he suddenly realized that he did.

" _Loki_? Loki's your dad?" He said, absolutely flabbergasted.

"What's so surprising about that?" Slepnir asked. "I understand you were told that he was a bit beyond a god, but gods are gods, and he _is_ one."

Percy had had no idea that Loki had children. Annabeth had probably found out when she'd looked him up, though. If only she were here...Percy shook his head to refocus. "So you're here because we helped him?"

"Your camp offered my father sanctuary when he had nowhere else to go." Slepnir shrugged. "We owe you greatly because of that. But I can't stay for long."

"What? Why not?" Percy asked, startled. "If you're here to help-"

"I have helped." Slepnir interrupted. "Only a little, but that's my part done. My brother has already offered help to another trio of questers. I don't doubt that you'll meet my siblings at one point or another."

Percy couldn't help but feel a bit cheated. He'd said he was here to help, but was going to leave right after saying that? "That doesn't make sense."

"It's a debt my entire family owes you, in a way." Slepnir explained. "Of course we're not going to pay it _all_ back individually, or else you'd end up owing _us_ the same amount four times over. Besides, you've got quite a challenge ahead of you, don't you? I'm sure you wouldn't want to waste all the aid you could call on now."

He had a point. "You're just leaving, then?"

"This is Roman territory." Slepnir said. "I'm no Roman. I'm not really a god, but...I'm out of place enough that it's a bit uncomfortable being here. If I stay long enough someone's bound to notice, and your gods can be _quite_ territorial." He smiled, giving Percy a two-fingered salute in a way that said he wasn't used to having hands. "I wish you luck."

He pulled his cloak around him and vanished, blurring into mist that quickly evaporated, leaving Percy staring at nothing.

It wasn't the weirdest thing that had happened to Percy - in fact, it barely made the list - but he couldn't help lingering over it.

Who else from the Norse pantheon was going to mysteriously appear and offer their help?

* * *

 **Read and review, guys! Bonus points to whoever can guess which of Loki's kids is going to show up next. I'll let you know if you're right!  
**


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